The inventor proposed a system using a combination of magnetic marks and a plurality of coils arranged as a coil array to continuously detect a position of a moving vehicle (Patent Publication 1: JP2002-337037A). There are constraints on the length of the magnetic marks. Therefore, in the Patent Publication 1, in use, the magnetic marks are continuously arranged without any gaps, and the magnetic mark to be detected is switched. Further, the length of a detection head having the coil array is shorter than the length of the individual magnetic marks, and the head is only affected by one magnetic mark.
However, it is difficult to provide the magnetic marks without any gaps along a long moving route. In an attempt to address the problem, the inventor studied a technique of providing magnetic marks at intervals, and detecting a position of a moving vehicle continuously without any gaps using a single detection head, and achieved the present invention.